Screen rooms



Oct. 2, 1956 E. A. LINDGREN SCREEN ROOMS 3 Sheets-Sheet 1 Filed Sept. 5, 1952 INVENTOR. CZ fZJZ BY E. A. LINDGREN Oct. 2, 1956 SCREEN ROOMS 3 Sheeis-Sheet 2 Filed Sept. 5, 1952 2, 19.56 E. A. LINDGREN I 2,765,362

SCREEN ROOMS Filed Sept. 5, 1952 I 5 Sheets-Sheet 3 United States Patent SCREEN ROOMS Erik A. Lindgren, Chicago, Ill.

Application September 5, 1952, Serial No. 308,136

9 Claims. (Cl. 174-35) The present invention relates to construction features of a demountable panel screen room or similar cubicle designed for the suppression or attenuation of radio waves.

This invention concerns itself more particularly with the problem of prefabricated demountable panel wall units having double layers of shielding material and the man ner whereby during assembly and disassembly electrical continuity is established between corresponding shielding layers in both adjacent wall panel elements as well as between contiguous enclosure walls which encompass the cubicles.

Various materials are recognized to possess shielding characteristics which well serve the purpose of isolating space units against electromagnetic as well as electrostatic wave penetrations. These materials are usually metallic and planar in form. Their shielding efficiency is related to their conductivity and non-permeability. Continuous electrical conductivity between contiguous points affords more pronounced efliciency as a radio wave shield in the intermediate and lower wave bands. By utilizing multiple mutually spaced shielding enclosures, the quality of wave attenuation may be improved and extended over a wider range of frequencies. The effectiveness of attenuation has been recognized as factorially dependent upon establishment of efficient impedance, in respect to double screen shields and for this purpose each screen is required to be maintained electrically insulated from the other. Since each screen is required to completely encompass the enclosure, one lying entirely within the other, there is thus presented a unique problem of conductivity coupling as between consecutive sections of the same screen and at the same time of securing isolation as between different screens.

It is accepted that in order to achieve very high attenuation, the screen should be made of a metal having high conductivity and yet possess adequate tensile strength to withstand outline suspension. The screen should be of a fine mesh in order to reduce as far as possible permeability. A double layer of 22 mesh copper screen wire or tinned iron wire will afford a satisfactory performance to secure an effective barrier against emanation or invasion byradio waves within the popular communication bands. The attenuation in logarithmic units through a shield layer has been evaluated as proportional to the first power of its thickness and to the square root of its conductivity, permeability and the wave frequency.

In recognition of these factors and particularly with the relative importance respecting low permeability in a screen enclosure, in order to achieve high impedance, it is a principal object of the present invention to provide a prefabricated screen room construction utilizing dual screen shields which are electrically insulated, one from the other, under all conditions of attachment as between the panels, but shall none the less effect positive edge to edge contactual engagement between panel sections respecting corresponding screen elements.

"For, a better understanding of this invention and for tural embodiments, attention will now be directed to the an explanation thereof in reference to particular struc-- accompanying illustrations in which corresponding parts are designated by like reference numerals throughout, and in which:

Fig. l is a perspective view of a multiple panel enclosure or cubicle having embodied therein various features of the invention.

Fig. 2 is a fragmentary detailed perspective view on an enlarged scale illustrating a manner of structural attachment between consecutive vertical wall panels.

Fig. 3 is an enlarged transverse sectional view taken approximately on line 3-3 of Fig. 1.

Fig. 4 is a fragmentary detail perspective view on an enlarged scale showing the corner construction of one of the end corner panels.

Fig. 5 is an exploded perspective view featuring the components which make up one of the springable edge screen angular arrangements, and

Fig. 6 is a transverse sectional view illustrating the structural features respecting a door panel in relation to one of the side walls.

Attention is now directed to the general showing in Fig.-

l of a prefabricated multiple panel enclosure housing in which one of the side walls designated generally 11 is framed to accommodate an entry doorway sealed by closure door 12. An end wall 13 constructed generally after the manner of the other side wall 11 is adapted to join with ceiling and floor panels as well as with the side wall panels to effect or complete the enclosure which, in order to be effective over a wider range of frequencies, requires a total encompassment by an internal screen layer or sheet and spaced therefrom an external screen layer. The two layers are required .to be physically spaced and electrically insulated, one from the other.

The end wall is illustrated as being made up of three panel sections indicated 14, 15, and 16, of which the central panel 15 is butt joined to the outermost panels 14 and 16 with the outer edges of the outermost panels lap fitted over the ends of the side wall panels, of which the visible one is designated 17. Panels 14 and 16 are indicated.

The particular arrangement of the various wall panels is not of primary importance to this invention. Accordingly, it is to be understood that the number of panels and their relative arrangement are factors susceptible to preference and extensive variation.

The basic concept of this invention revolves around the construction of each prefabricated unit panel and more particularly with regard to the unit panels which have been arbitrarily shown to make up the vertical walls of the cubicle in the illustrated examples. comprises two rectangular frame members of which the inner one is advantageously constructed of relatively wider framing material 18, Fig. 3, and the outer one of relatively narrower material 19. The outer dimensions of the two frames may be made identical so that the ceiling panels may then be employed after the manner exemplified in Fig. 3.

Between the two rectangular frames which comprise each one of the wall panels a shielding screen 21 is clamped serving the purpose of the outer wave barrier while on the inner surface of the inner frame as at 22 a similar screen is applied which constitutes the inner barrier. The shielding screens may be made of any metallic substance such as perforated or woven wire sheets dimensioned so as to afford sufficient fringe margins to be folded over the frame corners as at 24 and 25, then again infolded into the channels or peripheral troughs 26. These channels are rabbeted out of the framing wood in spaced relation to the surfaces which adjacently support the screens 21 and 22. 'When' employing iron"- -or copper wire. screen, the sheets may be preformed-on Each panel I creasing or bending forms or on a tinsmiths brake so that a band area 27 may result which will be supported by the upstanding rib 28.

After each frame has-been assembled and clamped together as by means of the countersunk securement bolts 31 which pass through sidewardly submerged threaded nuts 32 inserted through the sleeve apertures 33, the units will be sturdy, self-bracing and rigid and in readiness for assembling with other wall panels. The infolded fringe sections 34 which should be provided on all four sides of the panels are adapted to lie Within the grooves 26 conformingly so that when the filler strips 35 and 36 are driven into position as shown in Figs. 2 and 3, the band areas 27 will be given a slight transverse bowing effect with sufficient yield and springiness to permit this area to deform itself and take the shape of an adjacent surface against which it may be pressed.

In the same manner the screen area on the principal surfaces of the frame members will also how slightly as indicated in Fig. 5, particularly in the region just beneath the peripheral corners 24 and 25. With respect to the inside membrane 22 therefore, the screen surfaces will be permitted to undergo a moderate surface conformation when butting against a mildly irregular or sinuous juncture surface of a bordering panel.

These surface conformations are designed to accommodate for structural irregularities inherent with conventional panel assembly as exemplified by the ceiling unit designated 37, Fig. 4, and made up of the framing sections 38 and 39 having their shield screens as at if and 42. In these panels the screens, which may be formed of the same material as those of the vertical wall panels including copper or iron wire screen, are folded over the framing corners 43 and 44 on the one hand and 45 on the other. The skirting fringes of these ceiling panels are then stapled as at 46 to the under surface of frame member 33 and as at 47 to the edge surface of framing member 39. As a consequence of this form of securernent, the stapled areas become depressions and the juncture surface acquires a sinuous irregularity which, but for the aforedescribed conformation of the yieldable bands 27 would permit radio wave penetration or permeability, particularly in respect to higher frequencies.

By reason of the billowing and yieldable effects thus produced upon the hand area 27 as well as of the surface area adjacent to the corners as, for example, 25, this close conformity tends to fill out the sinuous distortions in the stapled fringe panels effectively preventing loss of wave attenuation on account of permeability.

The vertical wall panels are suggested to be made of framing material having different thicknesses 18 and 19 so that in the side to side attachment as suggested by the showing in Fig. 2, transverse clamping bolts 51 may be passed through aligned apertures and then drawn tightly together as by wing nuts 52 until a side wall of the required overall dimension is accomplished. In such cases the corresponding edges 27 of the adjacent wall sections, pressed against each other, will produce wiping engagement without serious distortion. This exemplifies the universal adaptability of the infolded edging construction to all types of joint arrangements.

Also, it is to be observed that the firm and stable anchor afforded by the strips 35 prevents unloosening and fraying of the screen, permitting screen houses which are intended to be dismantled and reassembled, to withstand the rigors of these operations Without manifesting failure. Further, it is to be observed that this construction permits the innermost screen to remain spaced from its outermost companion so that high impedance characteristics, upon which the success of these devices is so vitally dependent, may be effectively maintained.

In fact, with the embodiment shown, the attenuation accomplished is significant, the relation between the field strength measured outside of and the inside of shielded room is 1 to 14,100,000 within the measured frequency range of 10 to 43 megacycles. This corresponds to an attenuation of 123.1 decibels and up. Conventionally screen rooms on the market are only in the neighborhood of 40 to 50 decibels attenuation. The attenuation upon either side of this wave band referred to is even greater than the rating of 123.1 decibels.

In Fig. 6 there is illustrated a modified grooving practice with regard to a single framing timber 6i, grooved to receive the angular strips 62 and 63 on perpendicular surfaces of a door frame. Under these conditions of arrangement the ceiling frame 33 is advantageously reinforced by a framing strip 64 of spring copper having a free flange as at 65 like Weatherstrip, which is disposed to engage the springable band area as at 66. This permits the hinged panel which serves as a door barrier to form continuous and effective shielding with the flexible strip elements 64 and 67 under conditions which will ford active spring conformation and faithful contour shaping even under conditions of frequent separation.

While the present invention has been explained and described with reference to certain features of adaptability, it is to be understood nevertheless that the principles thereof are susceptible of considerable modification and variation. Accordingly it is not intended to be limited by the .illustrated examples in the accompanying drawings nor by the language chosen in the foregoing description excepting as indicated in the hereunto appended claims.

What is claimed is:

1. A wall panel construction for double screen shielding of radio Waves, comprising a unitary panel section having a pair of independent metallic screens each forming one of its face surfaces, the margin of each screen extending beyond the panel sides and being turned over the frame corners substantially normal to said face surfaces, mean for ecuring the turned margins of said screens in spaced parallel coplanar relation with each other to provide a pair of independent peripheral contact areas on said panel adjacent said corners, said contact areas being normally spaced from the underlying surface of said panel and providing a resiliently yieldable contact surface adjacent said corners adapted to make a continuous electrically conductive contact with related independent screen surfaces of contiguous boundary panels.

2. A panel construction for screen rooms which comprises a pair of frame elements secured together in face to face coextensive alignment, a screen extending entirely over one face of each of said frames, one of said screens being a wire mesh membrane clamped between said frames and each screen having perimetric extension beyond all frame side edges, each of said frame side edges having a longitudinal groove spaced a predetermined distance from its screen covered face, and the perimetric extensions of said screens being turned over the edges of the respective frames and inset into the respective grooves, whereby spaced parallel coplanar screen covered contact surfaces are provided on each edge of said panel for abutting engagement with corresponding contact surfaces on contiguous panels.

3. A panel structure for shielding a space against radio waves which comprises a pair of rectangular frame components secured together face to face, a screen membrane disposed between and coextensive with the abutting faces of said frame components, a second screen membrane disposed on an opposite face of one of said components, each of said membranes having a perimetric extension beyond the borders of said frame components, the edge surfaces of each of said frame components being perimetrically grooved in predetermined spaced relation with the plane of a respective one of said membranes, the perimetric extensions of said membranes being turned over the edges of the respective frame component and inset into a respective groove, and filler strips adapted to be secured within the grooves of said frame components to clamp the edge of the respective screen membrane therein and form an outward bulge in the portion of said membrane overlying the surface of the respective panel component along said frame edge and providing resilient electrical contact surfaces along said frame edges for engagement with a corresponding contact surface on contiguous panels.

4. A wall panel construction for attenuating radio waves comprising a pair of contiguous panels having rectilinear sides, and a pair of electrically independent metallic membranes for each panel, each membrane forming one of the face surfaces of a panel with the margins thereof extending beyond the edges of its respective side of the panel and being turned at right angles to said face surfaces, one of said panels having spaced channels into which the margins are turned, the turned margins of the membranes forming peripheral contact areas evenly spaced throughout their length on said panels along said turns, the contact areas on one panel being opposite the contact areas on the other panel for continuous electrically conductive contact under pressure between panels, and means for securing said contiguous panels tightly together in abutting relationship.

5. A wall panel construction for attenuating radio waves comprising a panel having rectilinear side members having spaced parallel channels therein, and a pair of electrically independent metallic membranes each forming one of its face surfaces with the margins thereof being turned at right angles to said face surfaces and received in said channels, the margins of the membranes forming evenly spaced peripheral contact areas on said panel along said channels for continuous electrically conductive con tact with corresponding margins of like membranes of contiguous boundary panels.

6. A wall panel construction for attenuating radio waves comprising a panel having rectilinear sides, and a pair of electrically independent metallic membranes each forming one of the face surfaces of the panel with the margins of the membranes extending beyond the edges of the respective sides of the panel and being turned at right angles to said face surfaces, the turned margins of the membranes forming evenly spaced peripheral contact areas on said panel for continuous electrically conductive contact with corresponding margins of like membranes of contiguous boundary panels.

7. A prefabricated panel construction for shielding enclosures against radio waves comprising, a panel made of two rectangular frame members butted face to face and having a sheet of metallic screen therebetween and another such sheet forming the outer face surface of one of the frame members, marginal portions of said screens extending beyond the frame sides, said frame members each having a perirnetric edge channel, and the marginal portions of each of said screens being turned over the frame corners and inset into a respective channel, anchor strips adapted to lodge in said channels to secure thereat the inset margins of said screens and provide spaced parallel outwardly bowed areas of said metallic screen adjacent said frame corners and extending peripherally around said panel edges, said bowed areas being adapted to make continuous electrical contact With the corresponding areas of adjoining boundary panels.

8. A panel construction for screen room enclosures which comprises, certain panel units comprising pairs of rectangular frames secured together face to face with separate metallic screen shields respectively disposed on one exposed face of and between said frames, the margins of said shields being folded over the corners of respective frames and into peripheral recesses spaced from the screen covered frame faces, the intervening band portions of the screen margin being bowed away from the frame edges to provide resilient contact surfaces adjacent the frame corners, and other panel units comprising pairs of rectangular frames also secured together face to face and having corresponding independent metallic screen shields mounted thereon, the margins of said other panel unit shields being turned over the frame edges and secured to the frame peripheries thereat, said contact surfaces of the peripheral screen portions of said certain panel units being adapted when engaging the corresponding peripheral screen portions of said other panel units during assembly of contiguous panels to form continuous conductive electrical contact between the corresponding independent screen shields of said panel units throughout the length of the adjoining panel edges.

9. A panel construction for attenuating radio waves comprising a rectangular frame member, a pair of electrically independent reticulated metal membranes disposed on opposite faces of said frame member, and having perimetric extensions beyond the frame side edges, the side edges of the frame having a longitudinal groove therein spaced a predetermined distance from one of its membrane covered faces, and the perimetric extension of said one membrane being turned over the edge of the frame member and inset into the groove whereby a membrane covered contact surface on the side edges of the panel is provided for abutting engagement with corresponding contact surfaces on contiguous panels, and means for securing the other membrane marginally to the frame in spaced relationship to said turned over edge of said one membrane.

References Cited in the file of this patent UNITED STATES PATENTS 547,585 Lusk et a1. Oct. 8, 1895 644,887 Barnes Mar. 6, 1900 974,380 Hoagland Nov. 1, 1910 2,405,987 Arnold Aug. 20, 1946 2,578,614 Sylvan Dec. 11, 1951 OTHER REFERENCES Publication I, ARRL Report No. 5-48. Specification and Design Characteristics for ARRL Screen-Room Model 1A and 1B. Published by U. S. Naval Air Development Center at Johnsville, Pa. August 11, 1947.

Publication II, NRL Report 3908 Measuring the Shielding Efiiciency of Screened Enclosures. Published by Naval Research Laboratory, Washington, D. C. Nov. 14, 1951. 

